Strong $hbox{LP}_{01}$ and $hbox{LP}_{11}$ Mutual Coupling Conversion in a Two-Mode Fiber Bragg Grating

摘要

A fiber Bragg grating is inscribed in a two-mode fiber using a 193-nm excimer laser and a phase mask. Strong $hbox{LP}_{01}$ and $ hbox{LP}_{11}$ mutual coupling as large as $-$ 22.5 dB, which corresponds to a modal conversion efficiency of more than 99%, is experimentally achieved. The intermodal coupling mechanism is theoretically analyzed through a finite element method. This device can be used as a low-cost reflective $hbox{LP}_{01} leftrightarrow hbox{LP}_{11}$ converter.